Cellulose saccharification



Filed Sept. 1'7, 1945 IN V EN TOR. Amie/s HERE/VG BY ATTORNEY Patented June '28, 1949 2,474,669 CELLULOSE SACCHARIFICATION Andr Hreng, Paris, France 7 Application September 1'7, 1945, Serial No. 616,831

' In France September 22, 1944 2 Claims.

This invention relates to a method for the continuous sacchariflcation of plants.

The principal methods used for the time being for the saccharification of woody material and all cellulosic wastes by acids are discontinuous methods. They require an intermittent working equipment which is very intricate. Their efliciency remains low because the losses are always high and the regularity of the products is not insured. Continuous methods are also known which comprise a diffusion operation requiring an important battery of diffusers the working of which necessitates an abundant and expensive staff.

All these methods, whether continuous or discontinuous, comprise a regeneration of the acids which have been used, which entails the necessity of putting into play special apparatuses often consisting of expensive materials such as rare metals, gold and platinum, for instance. Furthermore, they entail a very important consumption of energy and of heat.

It follows that all the known methods are expensive to install as well as to operate.

The present invention has for its object to provide a continuous method for the saccharification of plants by means of acid, which makes it possible to avoid these disadvantages and substantially to reduce the cost of the products derived and, more particularly, of alcohol, furfural and food yeasts.

Said method is characterized by the fact that the material, treated in a continuous circulation, is successively submitted to animpregnation by the liquid acid, to a treatment by the gaseous acid, which insures the concentration of the acid and the extraction of the sugars, and to a drying by the gaseous acid, which produces the recovery of the acid which has been used for the treatment.

All the difficulties arisin from the discontinuous method are avoided. The efliciency is improved, the regularity of the products is obtained. Furthermore, the use of gaseous acid renders possible a considerable reduction of the equipment and a very appreciable reduction of the labour and of the consumption of energy and of heat.

Said method is suitable for all vegetable materialssuch as wood chips, sawdust, peat, household refuse and, in general, for all cellulosic materials. It can be used with various acids such as hydrochloric, sulphuric, formic acid or any other suitable gaseous or liquid fluid.

The single figure of the appended drawing shows by way of example a diagram of the device used for carrying out the method according to the invention. The following description relates to the treatment of comminuted Wood with hytroduction of the wood. The latter when introduced into 2 is sprinkled with an excess of liquid hydrochloric acid. Said acid comes from the return 28 and from the vat 6 in which its concentration is adjusted. Said concentration varies accordin to the species of wood which is treated and Whether or not the extraction of the pentoses is effected by a prehydrolysis as will be seen later on. A preheater l2 makes it possible to bring the acid to the suitable temperature.

The wood descends progressivelyby a simple falling action into the impregnation vat 2 whereafter it passes into the hydrolysis tower 3. The latter can be of any kind such as, for instance, the so-called Gay-Lussac towers used in chemical industry. More particularly, it can be a tower of the kind which forms the subject-matter of the patent application Serial No. 616,830 filed on September 17, 1945. It is in the tower 3 that the continuous difiusion is effected, the wood impregnated with acid falling down from one stage to the following one.

At the bottom of the tower is a chamber 3? divided into two parts one of Which receives the gaseous hydrochloric acid supplied by the piping A while the other receives the treated material and the acid in excess flowing along the successive stages of the tower 3. A discharge tube for the acids in excess collects the latter and brings them to the vat l l.

Vat I0 is a fresh acid storage. I4 is a baromet- 'rical condenser with its cooler l3. Said condenser condenses the excess of hydrated hydrochloric gas and feeds the reservoir 10 from which .the acid returns to the cycle.

Vat II and circuit 21 make it possible to bring acid in excess into the tower 3 again and to concentrate it in acid and sugars.

A pump and pipe 8 carry the residue of the wood which chiefly consists of lignin impregnated with acid and sugars into the drying-room I5, the pipe 9 being used for the return of acid removed at the point 34 in the drying room IS. The latter is preferably constituted like the tower 3. In said tower the lignin falls down in a regular manner.

Through the samepasses a current of gaseous hydrochloric acid in a cold condition less than 30 C. whichconsists of anhydrous acid brought to the bottom of the drying-room through the piping l9 and leaving at the top of said room after having been loaded with water and acid. One thus sees that through the use of gaseous acid the drying is obtained in the cold and under the atmospheric pressure. Thus, every degradation of the sugars is avoided which beyond40 C. and in the presence of acid would be, converted and become useless; this result being obtained without it being necessary to operate in vacuo as in the known methods for the recovery of acid. Simultaneously, the acid contained in the lignin is recovered without special accessory apparatuses. The dried lignin is collected on the bottom of the dryingwhere a supplement coming from be added.

In the tower 3 the wood which is preferably maintained in a state of constant turbulence is submitted to the action of hydrochloric gas flowing through the same in a counter-current relation. Said gas which is introduced at 4 into the chamber 31 in the lower part of the tower leaves at the top of said tower through the piping 46 after having acted uponthe wood. -It has passed through all the wood layerswhichwere originally impregnated with acid of 27-33%. It is partially room 15. It passes into a washer it where the sugars are dissolved and carried ofl. The lignin rises through slightly sloping ducts underthe action of screws. A current of water runs down along the slope and flows several times upon the same while dissolving the sugars whereafter it is collected at It, as very concentrated juices.

The lignin is ejected at H.

The slightly acid juices collected at It are preabsorbed by said acid which, owing to this fact, is concentrated and the excess saturated with moisture leaves at 45. By this means the titre of the acid in the fibres of the wood themselves rises little by little and finally reaches about 41%. The treatment takes place in the absence of air,

the atmosphere of the tower 3 being saturated with hydrochloric gas.

The method makes it possible to use ordinary commercial acid, to concentrate it at will heated in an exchanger 20 and brought to autoclaves 2| where the inversion of non-fermentable sugars is effected with the presence of 2% chlorhydric acid.. The autoclaves are heated by steam coming from, the boiler 24.

The juices are then neutralized by a base in the vat 22 which is provided with a stirring device and brought to 18 Brix in order ,to-undergothe fermentation. In the vat I8 said juices have a concentration of 22 to 25 degrees Brix.

A room for the dehydration of the acid is shown on the right hand side of the figure.

Said room comprises vats 23 containing calcium chloride in an oversaturated solution. Said chlo- 'ride absorbs the'water contained in the acid and The dehydration vats 2:1 can be substituted" by a plate-furnished column or by any other similar device.

With the above described method all the intricate and expensive apparatuses used for recovering theaeid are dispensed with since the acid is extracted from the lignin itself at the ordinary temperature and the atmospheric pressure. The losses of acid are reduced to those which are necessary for the inversion at 2|.

The temperature of the acid gaseous fluid is maintained in the pipings and auxiliary apparatus aboveits dew-point so as to avoid condensations of acid, which makes it possible to use common metals for these devices. When it is not intended to effect the extraction of the pentoses the hacked wood discharged into the tower '2 is copiously sprinkled there with liquid hydrochloric acid of 20-21 degrees Baum. It

The drying gas,

without any special apparatus nor loss of time. The treated material is then dried at i5 by the gaseous acid, anhydrous and cold as already indicated.

When it is desired to extract the pentoses the comminuted wood introduced into the impregnation vat 2 remains there during 30 to minutes. The acidof vat 6 is a little more diluted and its temperature is higher at I2 than in the preceding operation. The time of retention the vat 2 or the capacityof-said vatmust'be sufficient in order to permit the partial hydrolysis of the carbohydrates and the formation of pentoses in presence of acid under the action of the heat. a

The juices and the wood flow regularly into the tower 3; Some of the upper stages of tower 3 are sprinkled with fresh acid or with water. The juices coming from this sprinkling are removed at 33 carrying with them the pentoses which have formed. A portion of said juices rises through'29 into vat 2 for being concentrated by a new passage and for limiting the action of the acid. The excess is removed at 30. Said excess is then absorbed by dried lignin and passes into a drying-room identical in construction with the drying tower 15 for the containedacid being passes through the vat 2 during about fifteen piping 28 and brought the'top' of the vat 2 there extracted down to 2%. After the washing of the lignin the juices containing the pentoses and the 2% of acid are treated in an autoclave for obtaining furfural or xylose.

In tower 3 the wood the pentoses of which have been extracted falls'down further and the rising current of gaseous acid rapidly concentrates the acid in order to permit the formation already described process. I

. I claim:

1. A continuous method of extracting the pen toses and hexosesfrom comminuted wood comprising the following steps: impregnating the wood by treating it with heated liquid hydrochloric acid of 27-33% concentration for 30 to 45 minutes, thereafter treating the wood with fresh liquid acid, extracting pentose containing liquid and treating the wood therewith at an earlier stage, subjecting the impregnated material to-a countercurrent of gaseous hydrochloric acid at atmospheric pressure, thereby raising the strength of the acid absorbed in the wood to 41%, drying the material with a current of anhydrous gaseous hydrochloric acid at lessxthan 30 C.,.

thereby reducing the acid absorbed in the wood e vat to not over 2%, washing the lignin hexose mixture remaining after the last step, to extract hexoses drying the remaining lignin, absorbing the pentose liquid previously collected with the lignin, extracting the pentoses by drying the ligmn pentose mixture with a current of anhydrous gaseous hydrochloric acid at less than 30 C. and washing the lignin pentose to obtain the pentoses.

2. A continuous method of extracting the pentoses and hexoses from comminuted wood which comprises the following steps: impregnating the .wood by sprinkling it with heated liquid hydrochloric acid of 27-33% concentration by weight for 30 to 45 minutes, sprinkling the wood with additional hydrochloric acid, collecting the pentose containing liquid extracted by this sprinkling, subjecting the remaining impregnated material to action by hydrochloric acid in a gaseous state at atmospheric pressure thereby raising the strength of the acid absorbed in the woodto 41% and producing hexoses, moving the material whfle drying it in the presence of a countercurrent 01' hydrochloric acid in a gaseous anhydrous '6 state at less than 30 0.. thereby reducing th acid absorbed in the wood to not over 2% and extracting water and acid, washing the materials to extract the hexoses, and recovering the used acid." f

ANDRE manna.

REFERENCES CITED The following references are of record in the Great Britain Octhlo, 1927 

